The present invention relates to a control apparatus and a control method, and more particularly to a control apparatus and a control method which are related to a data transmission and a transfer mechanism of a multiple gateway communication system.
The data transfer mechanism of the multiple gateway communication system can be assumed to be an on-demand routing protocol, but its one very important object is energy saving of a network system and how to extend the life of the network. AODV (Ad hoc on-demand distance vector) routing protocol is a typical on-demand routing protocol, and the conventional AODV achieves the energy saving object by creation and update of routing with the “minimum number of hops” used as a parameter, and reduction of the number of hops to simplify the structure of routing. However, the creation and update of routing by the above method cause that some network devices of the network are more susceptible to communications than other devices, the power for the network devices is consumed fast, and the life time of the entire network is reduced.
For such problems, some solutions are exhibited by a conventional technology. For example, JP-A-2009-159457 has proposed a mechanism that creates a routing table on the basis of information about a radio propagation condition and shuts down a wireless terminal configuring an unused communication route, thereby aiming to reduce power consumption of the entire Ad hoc network and to extend the life time.
Specifically, according to JP-A-2009-159457, a transmission source terminal device creates a routing table according to the received power of a relay device (gateway), a remaining battery level, position information, and a packet arrival rate. Among them, it is judged on the basis of the received power of the relay device that the relay device has stopped its operation or moved to outside of the wireless communication range. And, it is also judged on the basis of the remaining battery level of the relay device how long the relay device having a low remaining battery level can still operate. It is also judged on the basis of the position information of the relay device whether the relay device has stopped its operation or it has moved to outside of the wireless communication range. Last, a transmission condition of wireless signals with the relay device is judged on the basis of the packet arrival rate of the relay device. Thus, a routing table is created and the communication route is switched to secure that at least one communication route can be used, and the wireless terminal configuring the unused communication route is shut down. By the above technology, the power consumption of the entire Ad hoc network is reduced, and the life time of the entire Ad hoc communication system can be extended.
However, JP-A-2009-159457 leaves the following technical problems unsolved.
(1) JP-A-2009-159457 can reduce the power consumption of the entire multiple gateway communication system by shutting down the gateways configuring the unused communication route, but it does not consider a difference in power consumption generated during communications of individual gateways with adjacent gateways, and an adjacent gateway having low power consumption cannot be selected for communication by creating the routing table. Therefore, JP-A-2009-159457 cannot realize optimization in reduction of the power consumption of the whole configuring the multiple gateway communication system and the power consumption of the respective adjacent gateways of the multiple gateway communication system.
(2) JP-A-2009-159457 does not make reference to the data delay generated when the respective gateways configuring the multiple gateway communication system perform data transmission. That is, a data delay generated from a busy gateway is long and a data delay generated from the gateway in an idle state is short, but JP-A-2009-159457 cannot shorten the data delay by selecting the gateway in an idle state. Today, demands for a real time property of network communications are increasing higher and higher, and more strict delay threshold control is demanded when specially urgent data (such as fire alarm data involved in smart building control) is sent. However, it is apparent that JP-A-2009-159457 does not meet the above demands.
(3) JP-A-2009-159457 has no reference to the effective code rate at the time of performing data communication between the respective gateways. That is, in a case where the communication condition is poor or a communication distance between the gateways is long, a high forward error correction code rate is necessary to assure the reliability of data, but it decreases the effective code rate at the time of data communication, resulting in lowering the efficiency of data communication. However, JP-A-2009-159457 does not consider the creation of the routing table at the effective code rate.
(4) JP-A-2009-159457 uses the remaining battery level as an important parameter when the routing table is created, but the remaining battery level is applied to only a communication device for which a battery is used to supply power. Therefore, it is hard to apply JP-A-2009-159457 to the communication device which supplies power by means of a power source or another method.
As described above, for the multiple gateway communication system, both power consumption and data delay are very important elements. Demands for power consumption and data delay by the communication system are increasing higher and higher today, but a conventional technology represented by JP-A-2009-159457 cannot achieve both power consumption and data delay.
And, for the multiple gateway communication system, the effective code rate is also a very important element other than the power consumption and the data delay. Obviously, it is more impossible for the conventional technology represented by JP-A-2009-159457 to consider three items of power consumption, data delay and effective code rate at the same time.
And, for the multiple gateway communication system, it is possible to include not only the terminal that uses a battery to supply power but also a device that supplies power by a power source or another method. Therefore, the conventional technology represented by JP-A-2009-159457 is hardly applied to the multiple gateway communication system including a device that supplies power by anything other than the battery.